Nationwide association between ambient ozone and sudden cardiac arrests in South Korea

Abstract

Several studies reported the association between ambient ozone and out-of-hospital cardiac arrest (OHCA). However, due to the limited geographical scope of monitoring, existing research has not fully evaluated the nationwide risk or identified high-risk populations. We conducted a nationwide time-stratified case-crossover study to examine the association between short-term outdoor ozone exposure during the warm season (April–September) and OHCA in South Korea (2015–2019), with a machine learning ensemble model for ozone (R2 > 0.92). Among the total population (51,912 cases), ozone exposure was associated with OHCA (odds ratio [OR] per 10 ppb increase in ozone: 1.022, 95% CI: 1.009 to 1.034). Individuals aged 0–59 years (OR: 1.026, 95% CI: 1.005 to 1.047) and 60–74 years (OR: 1.024, 95% CI: 1.002 to 1.048) exhibited associations with ozone exposure, and the risk estimates were not statistically different from the risk of those aged 75 years or older. Males had a higher risk (OR: 1.030, 95% CI: 1.014 to 1.045) than females, based on the point estimates. Stratification analysis revealed that males aged 60–74 years with medical histories faced the highest point risk estimates of ozone. This study provides crucial evidence to support targeted interventions for high-risk populations.